Washington, April 26 -- A volunteer at the White House Correspondents' Dinner, describing the suspected gunman at the shooting incident, said he appeared to be assembling a long weapon in a largely unmonitored area near the terrace entrance where bar carts were being stored, mere moments before opening fire.

"He was in that room. he grabbed it out of a bag or something," she said, pointing that the weapon was "long" and "didn't look like a typical gun," she told the New York Post.

Partially shielded from view, the man appeared to assemble the weapon before suddenly moving towards the main event space. "He put it together and. ran towards the stairs to go down to the ballroom," she said, with gunfire breaking out within moments.

"It just ...